1. Technical Field
This invention relates generally to image capture devices, and more specifically to an image capture device using a rolling band shutter to correct for device motion while capturing images.
2. Background Art
Photography is experiencing an explosion in popularity due to advances in technology. Digital cameras and digital imaging are fueling a new interest in photography. Not too long ago, the only way to capture an image was to use a film camera. A user adjusted and aimed the camera at a subject, and then took the picture. The user then had no idea what the picture looked like until they removed the film from the camera, took the film to a processing center, and had the film developed.
Digital cameras have revolutionized photographic process. With a digital camera, one points and shoots, seeing the image appear instantly on a display without the need of developing film. What's more, when the picture fails to turn out as planned, the user simply deletes the electronic image from memory and shoots again. The efficiency and low cost associated with digital photography is very appealing to consumers. It is so appealing, in fact, that digital cameras are showing up on all types of electronic devices, including mobile telephones.
One problem associated with photography, however, is that of camera shake. Camera shake occurs when there is subtle movement of the camera while taking a picture. This movement can make a subject appear blurred or out of focus. The problem is most pronounced in low light conditions where image sensor exposure times are long. This problem is also exacerbated in digital photography because the cameras and devices are sometimes very small and very light. Lightweight devices that fit easily in a pocket, while great for portability, are sometimes difficult to hold perfectly steady while taking pictures, especially in low light conditions.
Turning now to FIG. 1, illustrated therein is a prior art digital image capture device 101 in the process of taking a picture. As indicated by line 102, the digital image capture device 101 moved slightly while capturing an image of the subject 103. This motion could have been due to motion in a user's hand, motion of a vehicle in which the user was riding, wind, or any other cause. Regardless of cause, the result is clear in image 104: the subject looks blurry and out of focus.
One prior art solution to the camera shake problem is to take multiple pictures of the subject. Once several pictures have been taken, the pictures can be averaged with one another to eliminate some of the blur caused by camera shake. The problem with this solution, however, is threefold: First, the process of taking multiple images requires a large amount of memory in which to store these images. Second, the process of taking multiple images takes time. Where the subject is animated, for example an animal or person, the subject may move during this multiple picture taking process. Third, as camera resolutions are commonly in the four to six megapixel range, averaging multiple six-megapixel images requires extensive processing power, which can add cost to the overall image capture device.
There is thus a need for an improved image capture device and method that compensates for camera shake with reduced memory and shorter exposure duration.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.